Electrode substrate, thin-film transistor, display and its production method

ABSTRACT

Using a lower electrode as a photomask, a yophobic region having generally the same pattern as that of the lower electrode and a yophibic region having a pattern which is generally the inversion of the lower electrode pattern are formed on an insulating film. A conductive ink is applied to the yophobic region and baked. Thus, an upper electrode having a pattern which is generally the inversion of the lower electrode pattern is formed in a self-alignment manner. Therefore no misalignment occurs even if a printing method is used. Thus, a semiconductor device such as an active-matrix thin-film transistor substrate can be fabricated by using a printing method.

TECHNICAL FIELD

The present invention relates to an electrode substrate in which a lowerelectrode and an upper electrode face each other with an insulating filminterposing therebetween and a semiconductor device using the electrodesubstrate such as a thin film transistor and a display device, and toproduction methods thereof.

BACKGROUND ART

An electrode substrate in which a lower electrode and an upper electrodeface each other with an insulating film interposing therebetweenincludes, for example, an electrode substrate used in a thin filmtransistor in an active matrix driving liquid crystal display device. Inthis electrode substrate, the lower electrode to be a gatewiring/electrode, a gate insulating film, and the upper electrode to bea source/drain electrode and signal wiring are formed in this mentionedorder through lamination on a substrate formed of glass or the like.High-precision formation, on a large-area substrate, of a thin filmtransistor and a display device driven by the thin film transistorrequires that the lower electrode and upper electrode to constitutewirings/electrodes and others each be fabricated into a fine pattern andbe disposed so as to be accurately aligned with each other. Accordingly,as a general method for fabricating the lower and upper electrodes,there is applied a so-called photolithography technique to use separatephotomasks for the upper and lower electrodes. In this method, aphotomask that has been beforehand finely fabricated is placed on a(positive type) photoresist deposited on an electrode; the photoresistis irradiated with light to remove the photoresist in the exposed area;the electrode is removed from the region not covered with thephotoresist to fabricate the electrode; and finally the photoresist isremoved. Accurate alignment of the photomask to be used in fabricatingeach of the electrodes, with respect to the substrate, makes it possibleto accurately align the pattern of each of the electrodes.

A backside exposure method is known as a method for accurately aligninga lower electrode and an upper electrode. The method concerned is amethod which auxiliarily utilizes “a part” of the lower metal electrodeas a photomask for specifying “a part” of the pattern of the upperelectrode. Details of this method are described, for example, inJapanese Patent No. 3,304,671 of the present inventor.

In these years, a method for producing electrodes by using a printingmethod, in place of a photolithography method, to be a so-calleddirect-drawing method, such as inkjet, plating, or offset printing, hasbeen actively studied as a method for forming the electrodes for use inthese electrode substrates, as described, for example, in NikkeiElectronics, No. 6.17, pp. 67-78, 2002. In these printing methods,required materials are disposed for electrode formation in requiredpositions. Accordingly, these printing methods are less in number ofproduction steps and higher in utilization efficiency of materials thana photolithography method, promising such an advantage that an electrodesubstrate can be formed at a low cost. The above cited referencedescribes a case where a metal wiring of 5 μm or less in wiring widthwas formed by an inkjet method, as a case of a fine electrode patternformed by a printing method.

A thin film transistor using the above described electrode substrate isapplied to an active matrix driving display device, and applied to aflat image-display device such as a display device in a laptop personalcomputer, a cellular phone or a flat television set so that used asdisplay elements are, for example, liquid crystal elements, organicelectroluminescence elements, electrophoresis elements or the like. Inaddition, there is a trend to apply a thin film transistor using theabove described electrode substrate to RFID typified by a contactless ICcard as a contactless information medium. In any one of these cases,such a thin film transistor is applied as a man-machine interfacedevice, through the intermediary of images and communicationinformation, to fundamental products that support the highlyinformation-based society.

DISCLOSURE OF THE INVENTION

In the above described prior arts, if in place of a photolithographymethod a printing method can be used as a method for forming anelectrode substrate in which a lower electrode and an upper electrode,which have fine patterns and are accurately aligned to each other, faceeach other with an insulating film therebetween, the number ofproduction steps will be drastically reduced and the utilizationefficiency of materials will be improved, promising an advantage that alarge number of electrode substrates can be formed at a low cost.

However, it has hitherto been difficult to apply a printing method,particularly as a method for forming electrodes, to the electrodesubstrate having the above described configuration, because of thefollowing reasons. Specifically, in an electrode formed by using aprinting method, “misalignment” is caused when an electrode with fineshapes is transferred onto a substrate from a printing device.Consequently, there is a problem such that even when at least one of alower electrode and an upper electrode formed on the lower electrodetrough an interposing insulating layer can be formed to have a finepattern by using a printing method, both of the electrodes cannot beaccurately aligned to each other. This problem will be described withreference to FIG. 12 illustrating the electrode misalignment problem inthe electrode substrate according to the present invention. FIG. 12 (a)shows a plan view illustrating an electrode substrate in which theelectrodes are well aligned to each other and a sectional view along theline A-A′; and FIGS. 12(b) to (d) are plan views illustrating electrodesubstrates in which “misalignment” is caused. A lower electrode 2, aninsulating film 3, and upper electrodes 5 and 6 are layered sequentiallyin this order on a substrate 1. In FIG. 12(a), both left and right edgesof the lower electrode 2 are aligned with the right end of the upperelectrode 5 and the left end of the upper electrode 6, respectively, ina manner well aligned with each other. On the other hand, FIG. 12(b)shows a case in which the lower electrode 2 undergoes a misalignment tothe lower right on the substrate surface; FIG. 12(c) shows a case inwhich the upper electrodes 5 and 6 undergo a misalignment to the upperleft on the surface of the insulating film; and FIG. 12(d) shows a casein which both of such misalignments are found. Even when the electrodesare finely formed, the occurrence of misalignment degrades thepositional aligning between the lower electrode 2 and the upperelectrodes 5 and 6, so that unnecessary overlapping and separationbetween the upper electrode and the lower electrodes are found. When aninkjet method is applied, such “misalignment” is known to occur while aconductive ink ejected from an inkjet head is flying until it adheres tothe substrate; and when a transfer printing method is applied, it isknown to occur when a pattern of a conductive ink is transferred fromthe transfer roll to the substrate.

Consequently, when an electrode substrate having the above describedconfiguration free from the defect of electrode misalignment is formed,it is necessary to apply a photolithography method at least to part ofthe steps; consequently, there is a problem that the reduction ofproduction steps and improvement of utilization efficiency of materialsare prevented. Additionally, there is a problem that when a thin filmtransistor and a semiconductor device such as a display device using thetransistor concerned are produced with the electrode substrate providedwith misalignment caused as a result of production by using a printingmethod, the devices are low in performance and uniformity, and cannot behighly integrated or cannot be of high definition.

In view of these problems, it is an object of the present invention toprovide an electrode substrate and a method for producing, by using aprinting method in place of a photolithography method, the electrodesubstrate in which a lower electrode and an upper electrode, having finepatterns and accurately aligned to each other, face each other in aself-aligned manner with an insulating film interposing therebetween,and to provide a thin film transistor and a semiconductor device such asa display device, using the above described electrode substrate, and amethod for producing the thin film transistor and the semiconductordevice.

As measures for solving the above described problems, a method to bedescribed below is used as a method for producing an electrode substratein which a light-nontransmitting lower electrode, a light-transmittinginsulating film having lyophobic/lyophilic regions on the surfacethereof and an upper electrode are layered sequentially in this order onthe substrate, the electrode substrate being characterized in that apattern of the lower electrode is approximately aligned with that of thelyophobic region on the surface of the insulating film; the upperelectrode is mainly formed on the lyophilic region other than thelyophobic region on the surface of the insulating film; and the patternof the upper electrode is a self-aligned shape formed by approximatelyreversing the pattern of the lower electrode. As a member for providingthe lyophobic region on the surface of the insulating film, there isused a photosensitive lyophobic film the property of which is convertedby light irradiation from the liquid repellent property that allows theliquid dropped on the surface to be repelled to the liquid attractingproperty that allows the liquid dropped on the surface to spread to wetthe surface. First, the above described photosensitive lyophobic film issubjected to pattern fabrication by means of a so-called backsideexposure method in which the lower electrode is used as a photomask andthe photosensitive lyophobic film is irradiated with light from thebackside of the substrate. More specifically, on the insulating filmsurface not light-shielded by the lower electrode, the photosensitivelyophobic film is removed to form the lyophilic region, and on theinsulating film surface light-shielded by the lower electrode, thephotosensitive lyophobic film portion having approximately the sameshape as that of the lower electrode remains to form the lyophobicregion. The upper electrode, characterized by having a pattern that isan approximately inversed shape of the pattern of the lower electrode,is formed in a self-aligned manner by dropping a conductive ink,containing at least one of a metallic ultrafine particle material, ametal complex and a conductive polymer as dispersed in a solvent, mainlyon the lyophilic region of the surface of this insulating film so as tocoat the region concerned and by baking the coated ink.

Additionally, there is formed a thin film transistor composed of anelectrode substrate and a semiconductor film, wherein the electrodesubstrate is characterized in that a gate electrode is formed as thelower electrode, and a source electrode and a drain electrode are formedas the upper electrode on two or more areas of the lyophilic regionseparated by the lyophobic region formed on the surface of theinsulating film in a pattern approximately aligned with the lowerelectrode so that the pattern of the upper electrode has anapproximately inversed shape of the gate electrode shape as the lowerelectrode, and the upper electrode is disposed in a manner self-alignedwith the gate electrode, the thin film transistor being characterized inthat the semiconductor film is formed so that the semiconductor filmcovers and extends across at least a part of each of the followingmembers on the above described electrode substrate, namely, the sourceelectrode, drain electrode and the lyophobic region (the gate electroderegion) interposing therebetween on the surface of the insulating film.

Additionally, there is formed an active matrix thin film transistorsubstrate composed of an electrode substrate and thin film transistors,wherein in the electrode substrate, a plurality of gatewirings/electrodes are formed as the lower electrodes, and a pluralityof signal wirings, a plurality of source/drain electrodes and aplurality of pixel electrodes are formed as the upper electrodes on thelyophilic regions separated into a plurality of regions by the lyophobicregion formed on the surface of the insulating film in a pattern that isapproximately aligned with the lower electrode, and wherein thesemiconductor films of the thin film transistors are formed so that thesemiconductor films extend to cover astride at least a part of each ofthe following members on the electrode substrate, namely, the sourceelectrodes, drain electrodes and lyophobic regions (gatewiring/electrode regions), on the surface of the insulating film,interposing between the source electrodes and the drain electrodes, theactive matrix thin film transistor substrate being characterized in thatthe thin film transistors each are disposed at any one of theintersection portions between the gate wiring and signal wiring.

Additionally, there is formed the active matrix thin film transistorsubstrate, characterized in that: a plurality of gate wirings/electrodesare formed adjacently to each other as the lower electrodes, wherein thegate wirings/electrodes are characterized by having a shape in which aplurality of adjacently disposed ring-shaped rectangles each having anopening are connected to each other at least at one or more locations;signal wirings and source/drain electrodes are continuously formed asthe upper electrodes, in a manner self-aligned with the above describedgate wirings/electrodes, in the spaces between the above describedrectangles so as to extend across the connection parts between the abovedescribed rectangles; and the pixel electrodes each are formed in one ofthe openings of the ring-shaped rectangles. In particular, there isformed an active matrix thin film transistor substrate, characterized inthat in the shape and configuration of the above described plurality ofgate wirings/electrodes, the widths of the individual connection partsconnecting the plurality of ring-shaped rectangles each having one ofthe openings in the gate wirings/electrodes and the separations betweenthe plurality of gate wirings/electrodes are smaller than those of theseparations between the plurality of ring-shaped rectangles each havingone of the openings forming the individual gate wirings/electrodes.

A photosensitive lyophobic monolayer film containing a carbon chain inwhich at least a part thereof is terminated with a fluorine or hydrogenatom is used as the photosensitive lyophobic film in place of thephotoresist.

Additionally, as a method for producing the electrode substrate havingthe above described characteristics, a photocatalytic material made oftitanium oxide, nitrogen-doped titanium oxide, strontium titanate or thelike, which displays photocatalysis with the light having thewavelengths that transmit through the substrate, insulating film andphotosensitive lyophobic film but do not transmit through the lowerelectrode, is disposed in the close vicinity of or is adhered to thesurface of a light-transmitting substrate on which light-nontransmittinglower substrate, a light-transmitting insulating film and aphotosensitive lyophobic film are layered sequentially in this order;and thus, backside exposure is carried out to decompose and remove thephotosensitive lyophobic film with the aid of the photocatalytic actiondisplayed by the photocatalytic material that absorbs the lighttransmitting through the substrate, insulating film and photosensitivelyophobic film, to fabricate the photosensitive lyophobic film so as tohave a pattern approximately the same as that of the lower electrode.When this method is applied, a material nontransparent to thephotosensitive wavelengths of the photosensitive lyophobic film may beused for at least one of the substrate and the insulating film. Thephotosensitive lyophobic film can also be fabricated so as to have apattern approximately the same as that of the lower electrode by using aso-called lift-off method, as a method other than this method, in whichthe photoresist formed on the insulating film is subjected to backsideexposure to be fabricated to form a pattern the same as that of thelower electrode, the photosensitive lyophobic film is layered thereon,and then the photoresist is removed.

The electrode substrate, thin film transistor, and active matrix thinfilm transistor substrate formed by the above described configurationand production method are used to form a liquid crystal,electrophoresis, or organic electroluminescence display device.Additionally, a semiconductor device such as an RFID tag device isformed by using the above described electrode substrate and thin filmtransistor in at least a part of the semiconductor device.

The present invention uses a method in which: a photosensitive lyophobicmonolayer film is used as a photosensitive lyophobic film as describedabove in place of a commonly used conventional photoresist; the abovedescribed photosensitive lyophobic monolayer film is exposed by usingthe lower electrode as a photomask to form a lyophilic/lyophobic patternon the surface of the substrate; and a conductive ink is coated on thelyophilic region of the substrate surface and baked to form the patternof the upper electrode. Because the pattern formation principlediscovered by the inventor is applied in this method, the shape of thelower electrode as the photomask to determine the approximate shape ofthe upper electrode exhibits such characteristics as described above.

Accordingly, the pattern formation principle applied in the presentinvention will be described below. First, the difference as aphotosensitive lyophobic film between the photosensitive lyophobicmonolayer film used in the present invention and a conventionalphotoresist will be described. Because the photoresist is generallylower in lyophobic property than the photosensitive lyophobic monolayerfilm, but can form a thick film of the order of 1 μm in thickness, alevel difference or bank is formed between a lyophobic region(photoresist portion) and a lyophilic region; this level differenceholds a conductive ink to form an electrode pattern. On the contrary,because the photosensitive lyophobic monolayer film is generally higherin lyophobic property than the photoresist, but forms a thin film ofabout 2 nm or less in thickness, the photosensitive lyophobic monolayerfilm cannot utilize such a level difference or bank effect as describedfor the photoresist and is characterized in that the lyophobic monolayerfilm concerned confines the conductive ink within the lyophilic regionswith the aid of the lyophobic effect to form an electrode pattern.

FIG. 11 shows the relation between the lyophilic/lyophobic patternsformed of a photosensitive lyophobic monolayer film and an electrodepattern formed by coating. The pattern formation principle applied inthe present invention will be described using this figure. FIGS. 11(1)to (3) show the conditions that electrode patterns of the same shape areformed on the basis of the three different lyophobic patterns, as can beseen from the plan views and the sectional views obtained by cuttingalong the A-A′ and B-B′ directions of the respective substrates. Theportion having a lyophobic film 4, formed of the photosensitivemonolayer film on the substrate 1 in each figure, forms the lyophobicregion, and the portion having no such lyophobic film forms a lyophilicregion. Here, a region in which, when pure water is dropped on asubstrate, a so-called contact angle between the substrate surface andthe drop of water is about 90° or more is defined as a lyophobic region,and a region having a contact angle of 45° or less is defined as alyophilic region.

In FIG. 11(1), the lyophobic region is of the ring shape having a closedouter periphery surrounding a rectangular lyophilic region inside thelyophobic region. When a conductive ink is coated on this lyophilicregion, the conductive ink does not wet and spread over the lyophobicregion but is confined within the lyophilic region. An electrode 5having the same shape as the above described lyophilic region isobtained by baking the ink thus confined. This is a general patternformation principle under which such an electrode can also be obtainedin the same manner when a photoresist is used as a lyophobic film.

In FIG. 11(2), as compared with FIG. 11(1), a part (a right center partin this figure) of the ring-shaped lyophobic region is cut by a long andthin lyophilic region. In this case, when a conductive ink is coated onthe rectangular lyophilic region, with almost all of the outer peripherythereof being surrounded by the lyophobic region, the conductive inkneither wets to spread over the lyophobic region in the same manner asin FIG. 11(1), nor penetrates into the cut part of the lyophobic region,and an electrode having approximately the same shape as in FIG. 11(1) isobtained by baking the thus coated ink. A necessary condition for theconductive ink not to leak from the cut part of the lyophobic region hasbeen found to require that the gap width of the part cut by thelyophilic region be smaller than the shortest width of the lyophilicregion (the short side for the rectangle shown in this figure). This isunderstood to be ascribable to a general property of liquid to bedescribed so that the dropped conductive ink tends to reduce the surfacearea (surface energy) so as to be as small as possible. Such an effectthat the conductive ink, namely, a liquid material held within arelatively wider lyophilic region, does not penetrate into a relativelynarrower lyophilic region connected to the above described relativelywider region will be hereinafter referred to as “the nonpenetrationeffect of conductive ink.”

On the other hand, in FIG. 11(3), as compared to FIG. 11(1), thering-shaped lyophobic region is linked with a long and thin lyophobicregion disposed in the central part thereof, to divide the rectangularlyophilic region surrounded by the lyophobic region into the upper andlower sections. Also in this case, when a sufficient amount ofconductive ink is coated on the rectangular lyophilic region, the outerperiphery thereof being surrounded by the lyophobic region, theconductive ink does not wet and spread over the outer-peripherylyophobic region in the same manner as in FIG. 11(1), but wets andspreads over the above described long and thin connection part of thelyophobic region, to connect the conductive ink sections coated on thetwo, namely, upper and lower lyophilic regions into one section, whichis baked to yield an electrode having approximately the same shape as inFIG. 11(1). A necessary condition for the conductive ink sections coatedon two lyophilic regions to be connected into one section by the flow ofthe conductive ink over the lyophobic region intervening between the tworegions has been found to require that the width of the long and thinlyophobic region intervening the lyophilic regions be smaller than theshortest width of the lyophilic region for dropping the conductive ink(short side for the rectangle shown in this figure). This is understoodto be ascribable to a general property of liquid to be described so thatthe dropped conductive ink tends to reduce the surface area (surfaceenergy) so as to be as small as possible by having one unified formrather than two divided forms. Such an effect that the conductive inksections, namely, liquid material sections held within two relativelywider lyophilic regions with a relatively narrower lyophobic regionintervening therebetween, are linked to form one unified region by theflow of the conductive ink over the above described narrower lyophobicregion will be hereinafter referred to as “the crosslinkage effect ofconductive ink.” This crosslinkage effect cannot be obtained when aphotoresist having level difference is used as a member for forming thelyophobic region, but can only be obtained when the photosensitivelyophobic monolayer film having almost no level difference is used as inthe present invention.

In the present invention, in order to form an upper electrode with aconductive ink, by taking advantage of the above described“nonpenetration effect of conductive ink” and “crosslinkage effect ofconductive ink,” the above described techniques are applied to the shapeof the photosensitive lyophobic film and to the shape of the lowerelectrode to be used as the photomask to determine the shape of thephotosensitive lyophobic film. The details concerned will bespecifically described in examples to be presented below.

According to the present invention, the pattern of the upper electrodehas a shape in which the lower electrode is approximately inversed owingto the above described effects, and the upper electrode is aligned withthe lower electrode in a self-aligned manner. Accordingly, when aprinting method such as inkjet printing capable of forming fine patternsis used as a method for forming a lower electrode, the upper electrodeformed by the printing method also comes to have a fine pattern, and isalso aligned with the lower electrode in a self-aligned manner.Consequently, it is possible to form an electrode substrate in which alower electrode and an upper electrode, having fine patterns and beingaccurately aligned with each other in a self-aligned manner, face eachother with an insulating film interposing therebetween, without using aphotolithography method, and to form a thin film transistor and asemiconductor device such as a display device, by using the electrodesubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows plan views and sectional views illustrating one example ofan electrode substrate and a thin film transistor of the presentinvention, and their production methods;

FIG. 2 shows plan views of a thin film transistor of the presentinvention prepared by a printing method;

FIG. 3 shows plan views and sectional views illustrating a 2×2 activematrix thin film transistor substrate of the present invention, and itsproduction method;

FIG. 4 shows plan views illustrating the shape relation between a lowerelectrode and a signal wiring/drain electrode of the present invention;

FIG. 5 shows a plan view illustrating the shape of a lower electrode(gate wiring/electrode) of the present invention;

FIG. 6 shows a plan view illustrating an m×n active matrix thin filmtransistor substrate of the present invention and its production method;

FIG. 7 shows a plan view illustrating an m×n active matrix thin filmtransistor substrate of the present invention and its production method;

FIG. 8 shows a plan view illustrating an m×n active matrix thin filmtransistor substrate of the present invention and its production method;

FIG. 9 shows a plan view illustrating an m×n active matrix thin filmtransistor substrate of the present invention and its production method;

FIG. 10 shows a sectional view illustrating an m×n active matrix thinfilm transistor substrate of the present invention;

FIG. 11 shows views illustrating the formation principle of coatedelectrode patterns with the aid of a photosensitive lyophobic monolayerfilm as applied in the present invention;

FIG. 12 shows plan views and a sectional view illustrating the problemof misalignment of electrodes in an electrode substrate;

FIG. 13 shows views illustrating a backside exposure patterning methodfor a photosensitive lyophobic film of the present invention;

FIG. 14 shows a plan view and a sectional view illustrating the maindevice configuration of a display device of the present invention;

FIG. 15 shows views illustrating a backside exposure method for aphotosensitive lyophobic film and its device configuration of thepresent invention;

FIG. 16 shows diagrams illustrating the effect of reducing the number ofsteps for producing an electrode substrate of the present invention;

FIG. 17 shows a plan view illustrating an m×n active matrix TFTsubstrate of the present invention and its production method;

FIG. 18 shows a plan view illustrating an m×n active matrix TFTsubstrate of the present invention and its production method;

FIG. 19 shows a plan view illustrating an m×n active matrix TFTsubstrate of the present invention and its production method;

FIG. 20 shows a plan view illustrating an m×n active matrix TFTsubstrate of the present invention and its production method;

FIG. 21 shows a plan view illustrating an m×n active matrix TFTsubstrate of the present invention and its production method; and

FIG. 22 shows a plan view illustrating an m×n active matrix TFTsubstrate of the present invention and its production method.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, several examples of the present invention will bespecifically described with reference to drawings. First, aphotopatterning method based on backside exposure of a photosensitivelyophobic film, to be a common technique, will be described withreference to FIG. 13.

First, there is prepared an electrode substrate in which a lowerelectrode 2, a light-transmitting insulating film 3 and a photosensitivelyophobic film 4 are layered sequentially in this order on alight-transmitting substrate 1. For example, a 1 mm thick quartzsubstrate is used for the substrate 1; a 140 nm thick Cr thin film isused for the lower electrode 2; a 400 nm thick silicon oxide film isused for the insulating film 3; a fluorinated alkyl silane couplingagent, typified by CF₃(CF₂)₇(CH)₂SiCl₃ and the like, that is a lyophobicmonomer having a carbon chain terminated with a fluorine group in atleast a part thereof is used for the photosensitive lyophobic film 4;and these are formed in the following methods respectively. The lowerelectrode 2 was formed by depositing a 400 nm thick Cr thin film at asubstrate temperature of 200° C. with a DC magnetron sputtering deviceand by subsequently processing it with a ceric ammonium nitrate solutionas an etching solution in a photolithography method (FIG. 13(a)). Theinsulating film 3 was deposited at a substrate temperature of 350° C. onthe basis of a plasma chemical vapor deposition method (plasma CVDmethod), with tetraethoxysilane (TEOS) and oxygen (O₂) as source gases.The photosensitive lyophobic film 4 was formed by thoroughly cleaningthe surface of the substrate 1 having the lower electrode 2 and theinsulating film 3 layered thereon sequentially in this order asdescribed above, and by coating, in combination with subsequent drying,a solution prepared by dispersing the above described silane couplingagent in a fluorinated solvent with spin coating, dip coating, sprayingor the like (FIG. 13(b)). The above described substrate was subjected toso-called backside exposure by irradiating the backside with the lightemitted by a low pressure mercury lamp for about 30 minutes (FIG.13(c)). The light irradiation path is indicated by arrows in the figure.On completion of the backside exposure, the photosensitive lyophobicfilm 4 was removed from the light-irradiated region (thenon-light-shielding region of the lower electrode) on the surface of theinsulating film 3 to form a lyophilic region, and the photosensitivelyophobic film remained on the non-light-irradiated region (thelight-shielding region of the lower electrode) on the surface of theinsulating film 3 to form a lyophobic region; and this was confirmed bythe following methods. The presence or absence of the photosensitivelyophobic film was identified by determining the presence or absence offluorine with photoelectron spectroscopy such as XPS and UPS, andTOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry). Measurementof the contact angle carried out by dropping pure water on the surfaceof the insulating film 3 gave a contact angle of 1000 to 1200 to thenon-light-irradiated region, but a contact angle of 30° or less to thelight-irradiated region. Dipping of the substrate into pure water andpulling the substrate out of the pure water gave the results that thepure water adhered only to the light-irradiated region(non-light-shielding region of the lower electrode) on the surface ofthe insulating film 3, and the overlapping width between the pure waterand the edge of the lower electrode 2 as observed in the directionvertical to the substrate was 1 μm or less.

From the above described results, it was verified that thephotosensitive lyophobic film 4 was fabricated so as to have a patternapproximately the same as that of the lower electrode 2 on the basis ofthe backside exposure method utilizing the lower electrode 2 as aphotomask (FIG. 13(d)).

In the following examples, the shape of the lower electrode 2 to be usedas a photomask is devised according to intended purposes to fabricatethe photosensitive lyophobic film so as to have a pattern approximatelythe same as that of the lower electrode 2. In this connection, the shapeof the lower electrode 2 and that of the photosensitive lyophobic film 4superpose each other in the plan views of the electrode substrate, sothat they cannot be presented so as to be identifiable in the plan viewsof the electrode substrate; accordingly, in the following figures, theset of reference numerals 2, 4 found in a figure means that thephotosensitive lyophobic film 4 is disposed above the lower electrode 2so as for the photosensitive lyophobic film 4 to have a shapeapproximately the same as that of the lower electrode 2. As for thesubstrate 1 and the insulating film 3, the set of reference numerals 1,3 is given in a plan view so as to have the same meaning.

EXAMPLE 1

FIG. 1 shows a plan view and a sectional view illustrating one exampleof an electrode substrate and a thin film transistor of the presentinvention and their production methods. The lower electrode 2 and theinsulating film 3 were layered sequentially in this order on thesubstrate 1, for example, with the same members and forming methods asin FIG. 13. However, in the present example, the pattern of a gateelectrode to be the lower electrode 2 had two openings disposedadjacently to each other. In the present example, because thephotosensitive lyophobic film 4 was coated by dip coating beforebackside exposure, the photosensitive lyophobic film 4 adhered to thesurface of the insulating film 3 as well as to the back surface of thesubstrate 1 (FIG. 1(a)). With backside exposure, the photosensitivelyophobic film 4 was removed from the back surface of the substrate 1 toform a lyophobic region having a pattern approximately the same as thatof the lower electrode 2 on the surface of the insulating film 4 (FIGS.1(b) and (c)). A conductive ink made of a liquid material containing atleast one of a metal ultrafine particle material, a metal complex and aconductive polymer, was coated on two lyophilic regions surrounded bythe lyophobic region, formed on the insulating film 3, and the coatingink was baked to form upper electrodes 5 and 6 (FIG. 1(d)). Noparticular constraint is imposed on the conductive ink, as long as theconductive ink is a liquid material having such properties that it isrepelled from the lyophobic region formed of the photosensitivelyophobic film 4 and it wets and spreads over the lyophilic region fromwhich the photosensitive lyophobic film 4 is removed, and exhibits asufficiently low resistance value after baking; specific examples ofsuch a material to be usable include a solution in which a metalultrafine particle material of about 10 nm or less in diameter or ametal complex, mainly composed of Au, Ag, Pd, Pt, Cu, Ni or the like, isdispersed in a solvent such as water, toluene or xylene. Further, forthe purpose of forming ITO (indium tin oxide) as a transparent electrodematerial, a solution in which a metal alkoxide such as In(O-i-C₃H₇)₃ orSn(O-i-C₃H₇)₃ is dispersed in a solvent such as water or an alcohol canbe used. Furthermore, as the transparent electrode material other thanthis, an aqueous solution of PEDOT (poly-3,4-ethylenedioxythiophene),polyaniline (PAn), polypyrrole (PPy) or the like doped with PSS(polystyrene sulfonic acid) being a conductive polymer can also be used.It was possible to form the upper electrodes 5 and 6 each having a filmthickness of about 100 nm with any one of the above described materialsby dropping them in an amount enough to cover the above described twolyophilic regions and then baking them at an appropriate temperature ofabout 80 to 500° C. under vacuum or in the air. In the present example,the upper electrodes 5 and 6 were formed as two rectangular shapes onthe lyophilic regions other than the lyophobic region on the surface ofthe insulating film, and the pattern was a self-aligned shape in whichthe pattern of the lower electrode 2 was approximately inversed.

In the above described example, Cr was used as the lower electrodematerial, but any other material nontransparent to the exposurewavelengths may be used. For example, Al, Mo, Au, Ag, Pd, Cu, or thelike may also be used. In the above described example, quartz, siliconoxide and a fluorinated alkyl silane coupling agent were used for thesubstrate 1, the insulating film 2 and the photosensitive lyophobic film4, respectively, but any other suitable materials may also be used;however, the materials for the substrate 1 and the insulating film 2 arelimited depending on the material for the photosensitive lyophobic film4, because they are required to transmit the exposure wavelengths of thephotosensitive lyophobic film 4. A fluorinated alkyl silane couplingagent was used as the material for the photosensitive lyophobic film,but other materials may also be used provided they are lyophobicmonomers each having a carbon chain terminated with a fluorine group inat least a part thereof; for example, oxetane derivatives, such asperfluorooxetane having a fluorine substituent in a side chain asdescribed in JP-A-2001-278874, may also be used. However, because theexposure wavelength of each of these materials for the photosensitivelyophobic film is 300 nm or less, the materials for the substrate 1 andthe insulating film 2 are required to be such materials that transmitthe wavelengths of 300 nm or less (having a band gap of 4 electron volts(eV) or more), and quartz and silicon oxide were used, respectively, inthe above described example. The silicon oxide film may also be a filmprepared with coating and baking in a so-called sol-gel method, inaddition to a film prepared with the plasma chemical vapor depositionmethod. In addition to silicon oxide, silicon nitride (Si₃N₄), siliconoxynitride (SiON), aluminum oxide (Al₂O₃) or zirconium oxide (ZrO₂) mayalso be used. The material for the substrate 1 may also be syntheticquartz.

Methods for alter the photosensitive wavelengths of the photosensitivelyophobic film to be longer wavelengths of 300 nm or more include thefollowing two methods. One is a method which uses a photosensitivelyophobic film made of a molecule having a dye group thermallydecomposable through absorbing the light having a wavelength of 300 nmto 700 nm; specific examples of such a molecule include the followingcompounds 1 and 2:

Methods for synthesizing these compounds will be described below.

(Synthesis of Compound 1)

Compound 1 was synthesized by the following reactions (i) to (iii).

(i) Reduction of Lyophobic Material

Krytox 157FS-L (50 parts by weight) manufactured by Du Pont Corp.(average molecular weight 2500) was dissolved in PF-5080 (100 parts byweight) manufactured by 3M Corp. The solution was added with lithiumaluminum hydride (2 parts by weight) and heated at 80° C. under stirringfor 48 hours. The reaction solution was poured into ice water, and thelower layer was separated. The separated lower layer was washed with 1%hydrochloric acid, and then washed with water until the washings becameneutral. After removing water in the washed solution by filtering with afilter paper, PF-5080 was evaporated with an evaporator to obtaincompound 3 (45 parts by weight) in which the terminal of Krytox 157FS-Lwas converted into CH₂OH.

[Formula 3]F—{CF(CF₃)—CF₂O}_(n)—CF(CF₃)—CH₂OH  Compound 3(ii) Reaction for Introducing Dye Skeleton

Compound 3 (45 parts by weight) was dissolved in HFE-7200 (100 parts byweight) manufactured by 3M Corp. The solution was added with ReactiveYellow 3 (another name: Procyon Yellow HA) (12 parts by weight), ethanol(100 parts by weight) and sodium carbonate (2 parts by weight) andrefluxed for 30 hours. The structure of Reactive Yellow 3 is shownbelow.

The solvents (HFE-7200 and ethanol) in the reaction solution wereevaporated with an evaporator. The residue was added with a mixture ofHFE-7200 (100 parts by weight), 35% by weight hydrochloric acid (100parts by weight) and ice water (100 parts by weight), vigorously stirredand then allowed to stand at rest. The lower layer was separated andwashed with water until the washings became neutral. After removingwater in the washed solution by filtering with a filter paper, HFE-7200was evaporated with an evaporator to obtain compound 4 (45 parts byweight) in which Reactive Yellow 3 was bonded to compound 28.

(iii) Reaction for Introducing Binding Site

Compound 4 (45 parts by weight) was dissolved in HFE-7200 (100 parts byweight). On cooling of the resultant solution to around 0° C., thesolution was added with Sila-Ace S330 (10 parts by weight) manufacturedby Chisso Corp., N,N-dicyclohexylcarbodiimide (10 parts by weight), anddichloromethane (20 parts by weight), and stirred for 3 hours. Thereaction solution was made to again get back to room temperature, andfurther stirred for 30 hours. The reaction solution was allowed to standat rest, and thereafter, when the reaction solution was separated nearlyinto two layers, the lower layer was separated. It is to be noted that aturbid layer produced between the upper and lower layers was not addedto the lower layer. The lower layer was washed with dichloromethane (20parts by weight) a few times and then filtered with a filter paper.Then, the solvent (HFE-7200) in the solution was evaporated with anevaporator to obtain target compound 1 (40 parts by weight).

(Synthesis of Compound 2)

Compound 2 (40 parts by weight) was obtained in the same manner as inthe synthesis of compound 1, except that Mikacion Brilliant Blue RS (7parts by weight) was used in place of Reactive Yellow 3 (12 parts byweight).

The chemical structure of Mikacion Brilliant Blue RS is shown below.

The sodium sulfonate part is sometimes converted into the sulfonic acidpart, and then it is converted into a sodium sulfonate part with sodiumhydroxide or the like before use.

When above described compounds 1 and 2 are used for the photosensitivelyophobic film, the substrate 1 and the insulating film 3 may onlytransmit any wavelengths within the above described wide wavelengthrange. Accordingly, as an inorganic material for the insulating film 3,in addition to a thin film made of silicon oxide (SiO₂), there may beused a thin film having a thickness of 300 nm made of tantalum oxide(Ta₂O₅), zirconium oxide (ZrO₂) or lanthanum oxide (La₂O₃), wherein thethin film is formed with the plasma chemical vapor deposition method orthe sol-gel method. Additionally, as an organic material for theinsulating film 3, there may be used a spin-coated film ofpolyvinylphenol (PVP) or polymethylmethacrylate (PMMA). For thesubstrate 1, there may be used a common glass substrate such as Corning1737 or various plastic substrates.

Another method for altering the photosensitive wavelengths of thephotosensitive lyophobic film 4 to be longer wavelengths uses aphotocatalytic material at least in a part of the insulating film 3. Thephotocatalytic material has the effect of absorbing light to produceholes and electrons having strong oxidizing and reducing power in thefilm to decompose organic materials to be adjacent to the photocatalyticmaterial.

In this case, all the above described materials can be used for thephotosensitive lyophobic film 4. For example, a photocatalytic materialcomposed of, for example, titanium oxide (TiO₂) is coated with a sol-gelmethod to form a film having a thickness of about 10 nm between theinsulating film 3 and the photosensitive lyophobic film 4 as describedby Tadanaga and Minami in Material Integration, 14(10), pp. 9 to 13(2001). Because titanium oxide absorbs the light having a wavelength of400 nm or less to cause photocatalysis, materials transmitting the lighthaving a wavelength of 400 nm or less can be used for the substrate 1and the insulating film 3. In this case, for the substrate 1, there maybe used a glass substrate or a plastic substrate made of polyimide orthe like high in light transmittance. For the insulating film 3, theremay be used the above described inorganic materials; however, it isrecommended not to use organic materials because they are decomposed bythe photocatalytic material.

This is also the case for a semiconductor material 7 to be describedbelow, and it is also recommended not to use organic materials for thesemiconductor material 7. When there is used, as a photocatalyticmaterial, a so-called visible-light-responsive photocatalytic materialwhich absorbs visible light of wavelengths of 600 nm or less to causephotocatalysis, materials that transmit the light of wavelengths of 600nm or less can be used for the substrate 1 and the insulating film 3.Consequently, all the above described inorganic materials can be used.

Among methods for fabricating the photosensitive lyophobic film 4 with aphotocatalytic material other than the above described materials, amethod which allows organic materials to be used for the insulating film1 and the semiconductor material 7 will be described in Example 6.

A thin film transistor can be fabricated by forming the semiconductorfilm 7 on the electrode substrate formed as described above of thepresent invention so that the semiconductor film 7 extends to coversastride at least a part of each of the source electrode 5, the drainelectrode 6 and the surface of the insulating film having the gateelectrode 2 on the under side thereof. The following materials andproduction methods can be applied for the semiconductor film 7. Thesemiconductor film 7 is obtained as follows: an amorphous silicon filmhaving a thickness of about 200 nm is formed as an inorganic materialwith the plasma chemical vapor deposition method at a substratetemperature of 250° C., with silane and hydrogen (SiH₄+H₂) as sourcegases; and thereafter, the amorphous silicon film is processed into anisland-like shape by dry etching with SF₆ as an etching gas on the basisof the photolithography method to obtain the semiconductor film 7. Thisfilm may also be subjected to laser annealing to yield a polycrystallinesilicon film. When inorganic materials are used for the semiconductorfilm 7 as described above, it is also desirable to use inorganicmaterials such as silicon oxide and silicon nitride for the insulatingfilm 3. Removal of the photosensitive lyophobic film from the surface ofthe insulating film 3 before forming the semiconductor film 7 serves tostabilize the interface between the insulating film 3 and thesemiconductor film 7, and thus provides good transistor characteristics.For example, a use of amorphous silicon has provided performancescomparable with those of common thin film transistors so that the fieldeffect mobility is 0.5 cm²/Vs, the threshold voltage is 2 V, and theon/off current ratio is of 7 digits. When organic materials are used, inparticular, when low-molecular weight substances are used, thesemiconductor film 7 is formed with vacuum deposition of an acenematerial, typified by pentacene and thiophene oligomers, at a substratetemperature from room temperature to 100° C. Mask deposition orphotolithography using oxygen as the etching gas is used to form thesemiconductor film 7 to be processed into an island-like shape. In caseof pentacence, a pentacene precursor or pentacene derivative is used asa material soluble in a solvent such as toluene or chloroform, and thus,a film can be formed by a coating method such as casting, spin coatingor dip coating. When polymeric materials are used, a film can be formedby the above described coating methods with any one of the followingpolymers: polythiophenes such as poly-3-hexylthiophene (P3HT) having aregio-regular structure (having the orientation in which the whole chainaligns in the same direction with head and tail adjacent to each other)that is a highly regular nano-structure, polyfluorenes such as acopolymer of fluorene-bithiophene (F8T2), and polyphenylenevinylene(PPV). With an organic material used for the semiconductor film 7, thetransistor characteristics are improved when the photosensitivelyophobic film 4 above the gate electrode 2 is not removed and thesemiconductor film 7 is formed on the photosensitive lyophobic film 4.For example, a pentacene deposited film formed on the photosensitivelyophobic film 4 exhibited such performances that the field effectmobility was 1.0 cm²/Vs, a threshold voltage was −2 V, and the on/offcurrent ratio was of 7 digits. However, when a pentacene deposited filmwas formed on the insulating film from which the photosensitivelyophobic film 4 had been removed, the performances were degraded suchthat the field effect mobility was 0.2 cm²/Vs, the threshold voltage was−5 V, and the on/off current ratio was of 4 digits. This is conceivablybecause the photosensitive lyophobic film 4 has an effect of improvingthe orientation order of the organic semiconductor material.

EXAMPLE 2

In this example, the case in which the lower electrode 2 is formed witha printing method such as an ink jet method and the semiconductor film 7is formed with a casting method will be described with reference to FIG.2 showing a plan view of a thin film transistor. For the lower electrode2, the same material and printing method as those used for the upperelectrodes 5 and 6 in Example 1 can be used. For the members other thanthe lower electrode 2, the same materials and methods as those used inExample 1 can be used. When an ink jet method is used, the lowerelectrode 2 to be the gate electrode takes on a shape in which dots aresequentially connected to each other as shown in the figure. This isbecause the conductive ink ejected from the ink jet head isotropicallyspreads to wet the uniform substrate 1 while retaining the trace of adot shape formed at the time of ejection. In the present invention, evenwhen the shape of the lower electrode 2 is deformed as described abovedepending on the fabrication method, the photosensitive lyophobic filmpattern having a pattern approximately the same as that of the lowerelectrode 2 is formed on the insulating film 3 in a self-aligned manner;consequently, the upper electrodes 5 and 6 each can be formed on theinsulating film 3 so as to have a pattern approximately the same as theshape obtained by reversing the shape of the lower electrode 2. WhenP3HT, for example, is coated, to form a film, on the upper electrodes 5and 6 with a casting method, the semiconductor film 7 is formed in amisaligned position (the figure shows an example shifted in anupper-right direction) as the case may be. Even when such a misalignmentis caused, the thin film transistor of the present invention provideduniform switching characteristics. This is due to the following reason.Generally, the thin film transistor characteristics vary to becomenonuniform depending on the variations of the parasitic capacitanceformed by the member sandwiched between the lower electrode 2, to be thegate electrode, and the upper electrodes 5 and 6, to be the source/drainelectrodes. In a common thin film transistor structure, there is adopteda so-called top-contact structure in which the upper electrodes 5 and 6are formed on the semiconductor film 7. In this connection, when theupper and lower electrodes and the semiconductor film undergomisalignment, the parasitic capacitance varies to make thecharacteristics nonuniform. On the other hand, in the present invention,the upper and lower electrodes are formed in a self-aligned manner toinhibit misalignment; the present invention also adopts a so-calledbottom-contact structure in which the upper and lower electrodes areformed first and then the semiconductor film 7 is formed on the upperelectrodes, so that the semiconductor film 7 is not sandwiched betweenthe upper and lower electrodes and does not thereby contribute to theparasitic capacitance. Consequently, the thin film transistor of thepresent invention provides uniform thin film transistor characteristicseven when the upper and lower electrodes 2 and 4 and the semiconductorfilm 7 are formed with a printing method. Formation of the insulatingfilm with a printing method makes it possible to form all the members onthe basis of printing methods to provide a thin film transistor havinguniform characteristics.

EXAMPLE 3

In the present example, a 2 row 2 column active matrix thin filmtransistor substrate composed of four thin film transistors formed atthe intersections between the two gate electrode wirings forming atleast a part of the lower electrodes and the two signal wirings formingat least a part of the upper electrodes, and a method for producing thesubstrate concerned will be described with reference to FIG. 3 showingthe related plan views and sectional views. The materials and theforming methods for respective layers of the present example are thesame as those in Examples 1 and 2, so that they will not be describedunless particularly required otherwise.

In the present example, for the purpose of utilizing the above described“nonpenetration effect of conductive ink” and “crosslinkage effect ofconductive ink” to form the signal wirings/drain electrodes and thesource electrodes/pixel electrodes, the shape having the features shownin FIG. 3(a) is adopted as the pattern of the lower electrode 2 formainly composing gate wirings/electrodes. Specifically, two gatewirings/electrodes, each being characterized by having a shape in whichadjacently disposed two ring-shaped rectangles 8 each having an openingare connected at one connection part 9, are disposed adjacently to eachother through a space 10 interposing therebetween. A rectangular gateterminal 11 is connected at the left edge of the gate wirings/electrodes5. Terminal forming lower electrodes 12 to be utilized for forming theterminals of the signal wirings/drain electrodes 5 are adjacently placedat the upper and lower portions of the two gate wirings/electrodesthrough the spaces 10 interposing therebetween. Particularly, byutilizing, as the shape of the lower electrode 2, a shape in which thewidth (a in FIG. 3(a)) of the connection part 9 of the gatewiring/electrode and the width (b in FIG. 3(a)) of the space 10 betweenthe gate wirings/electrodes and between the gate wiring/electrode andthe terminal forming lower electrode 12 were smaller than the width (cin FIG. 3(a)) of the space between the adjacent ring-shaped rectangles 8each having an opening, a conductive ink was coated along the spacebetween the rectangles and the coated ink was baked, and there wasformed an upper electrode 5, to function as a signal wiring and a drainelectrode having a linear shape to be continuously formed by extendingover the connection part 9 and disposed along the space between theabove described rectangles 8. When a conductive ink was coated on theopening to be the lyophilic region of the ring-shaped rectangle 8 andthe coated ink was baked, there was formed an upper electrode 6 tofunction as a source electrode and a pixel electrode in a self-alignedmanner (FIG. 3(b)). There was completed the active matrix thin filmtransistor substrate in which four thin film transistors were disposedon the respective intersections of the gate wirings/electrodes 2 and thesignal wirings/drain electrodes 5, by forming the semiconductor films onthe above described electrode substrate so that the semiconductor filmsextended to cover astride at least a part of each of the signalwirings/source electrodes 5 and the drain electrodes/pixel electrodes 6,on the electrode substrate, and the surface of the insulating film,interposing between the electrodes 5 and 6, having the gatewirings/electrodes 2 in the lower part thereof. The point of the presentexample resides in that the width of the space between the rectangles 8,namely, the width c of the upper electrode is set so as to be wider thanthe width a of the space 10 and the width b of the connection part 9 sothat when coating and forming the upper electrode 5 to be the signalwiring/drain electrode by using the conductive ink, the short circuitbetween the upper electrodes 5 may not be caused by penetration of theconductive ink into the space 10 between the gate wirings/electrodes 2,the upper electrodes 5 may not be disconnected by the failure of theconductive ink in spreading over the connection part 9, and the upperelectrodes 5 may thereby be formed to be continuous along thelongitudinal direction, by taking advantage of the “nonpenetrationeffect of conductive ink” and the “crosslinkage effect of conductiveink.” Specifically, the above advantageous effect was provided bysetting such that a=b=3 μm in relation to c=15 μm.

The plan view illustrating the relation between the shape of the lowerelectrode and the shape of the signal wiring/drain electrode is shown inFIG. 4. FIG. 4(a) shows the case in which the width b of the space 10was nearly equal to or larger than the width c of the upper electrode 5,wherein the conductive ink penetrated into the space 10 to cause theshort circuit between the adjacent upper electrodes 5. FIG. 4(b) showsthe case in which the width a of the connection part 9 was nearly equalto or larger than the width c of the upper electrode 5, wherein theconductive ink did not extend over the lyophobic region on theconnection part 9 to cause disconnection. Increase of the width a of theconnection part 9 as shown in FIG. 4(b) decreases the resistance of thegate wiring/electrode, and accordingly, this increase is favorable for athin film transistor substrate to be used for a display device. As acountermeasure against this disconnection, FIG. 4(c-1) shows a case inwhich the conductive ink is re-coated on the connection part to secureconnection. At this time, it is recommended that the photosensitivelyophobic film is removed with a HeCd laser or the like beforere-coating and a conductive ink having a relatively higher viscosity isused. However, there is a problem in that a modification according tothis technique requires time.

It is possible to form the upper electrode 5 or the signal wiring/drainelectrode 5 without disconnecting the connection part 9 irrespective asto the magnitude of the width a of the connection part 9, after removingthe photosensitive lyophobic film from the surface of the connectionpart 9 by irradiation with an ultraviolet laser or the like.

FIG. 4(c-2) shows a case in which a countermeasure to prevent adisconnection failure involves the shape of the lower electrode, whereina plurality of connection parts 9 are provided (3 parts in the figure),and even when the total width of the connection parts 9 is equal to orlarger than the width c of the upper electrode, the width of each of theconnection parts is made equal to or less than the width c of the upperelectrode. Herewith, the conductive ink can extend over the individualconnection parts owing to the “crosslinkage effect of conductive ink” toprevent the disconnection of the upper electrode 5 and at the same timethe gate wiring/electrode can reduce the resistance. Specifically, thedisconnection occurred for one connection part having b=15 μm inrelation to c=15 μm, but crosslinkage occurred to prevent thedisconnection for three divided connection parts each having a width of5 μm.

FIG. 4(c-3) shows a case of the lower electrode shape in which thering-shaped rectangle is recessed inward at the connection part 9 so asto locally increase the width c of the upper electrode, wherein thewidth c can be made larger than the width a of the connection part 9, sothat the “crosslinkage effect of conductive ink” is enhanced to allowthe signal wiring part of the upper electrode to be formed withoutsuffering from disconnection.

In the examples shown in FIGS. 3 and 4, in the individual gatewirings/electrodes 2, the adjacently disposed ring-shaped rectangles 8each having an opening are disposed so that the upper and lower edgesthereof were aligned horizontally. However, the present invention needsnot be limited to this case. For example, as shown in FIG. 5, there maybe adopted a configuration in which pluralities of the rectangles 8 aredisposed so that the individual pluralities of the rectangles 8 arealternately displaced up and down. It has been confirmed that because inthis case, the space 10 between the gate wirings/electrodes do notintersect linearly with the space between the rectangles 8 in which thesignal wirings are to be formed, this configuration has the effect toprevent the failure that when a conductive ink is dropped on the spacebetween the rectangles 8, the ink flows into the space 10 in both rightand left directions to cause disconnection or short circuit. In thisway, it is possible to suppress the disconnection failure and the shortcircuit failure of the signal wirings formed with a coating process, notonly by taking advantage of the nonpenetration effect of conductive inkthrough reducing the width of the space 10 as described above but bydevising the shape of the gate wirings/electrodes.

As described above, it was possible to form an active matrix thin filmtransistor substrate in which a thin film transistor is disposed on thegate wiring/signal wiring intersection, by forming an electrodesubstrate in which a gate wiring/electrode faced a signal wiring/drainelectrode and a source electrode/pixel electrode in a self-alignedmanner through an insulating film interposing therebetween. When themethods described in Examples 1 and 2 are used, the active matrix thinfilm transistor substrate can be fabricated exclusively by usingprinting methods.

Finally, the conductive ink material for forming the upper electrodes 5and 6 will be mentioned. When this substrate is used for alight-transmitting display device, the pixel electrode/source electrode6 needs to be transparent, so that the coating-type ITO material or theconductive polymer materials described in Example 1 are used. When thissubstrate is used for a reflective display device, it is effective touse Ag or the like having a high reflectance in the visible lightwavelength region for the purpose of improving the display performance.

EXAMPLE 4

In the present example, an m-row n-column active matrix thin filmtransistor substrate composed of m×n pieces of thin film transistorsformed at the intersections of m pieces of gate electrode wirings whichform at least a part of the lower electrodes and n pieces of signalwirings which form at least a part of the upper electrodes, and a methodfor producing the substrate concerned will be described below withreference to FIGS. 6 to 9 each showing a plan view and FIG. 10 asectional view thereof. The basic configuration is the same as that inExample 3. First, m pieces of gate wirings/electrodes 2, in each ofwhich n pieces of ring-shaped rectangles each having an opening areadjacently disposed and connected to each other at least at one or moreconnection parts 9 (two connection parts in the present example), areadjacently disposed to each other through spaces 10 (FIG. 6).Particularly, when the width b of the space 10 and the width a of eachof the connection parts 9 are made to be equal to or smaller than thespace c between the ring-shaped rectangles each having an opening, it ispossible to form n pieces of upper electrodes 5, which function as thesignal wirings/drain electrodes, in a linear shape continuouslyself-aligned with the lower electrodes in a manner extending over thelyophobic regions on the connection parts 9, by coating a conductive inkon the space c and baking it. The penetration of the conductive ink intothe spaces 10 to short the upper electrodes 5 to each other will notoccur.

Additionally, in the present example, an integrally formed lowerelectrode 12 for forming terminals is disposed so as to surround theouter periphery of m pieces of the gate wirings/electrodes 2 as a partof the lower electrode 2. For the purpose of preventing the formation ofthe upper electrodes 5 at the edge of the substrate 1 outside the lowerelectrode 12 for forming terminals, a sealing mask may be applied onthis portion, and may be removed after forming the upper electrodes 5.Furthermore, in the present example, the width of the signal terminalpart 13 for the lower electrode 12 for forming terminals was set to belarger than the width c of the upper electrode. The reason for this isthat the contact resistance with the signal circuit to be describedhereinafter is decreased by increasing the area of the upper electrodeterminal, and the signal terminal part 13 is also used as ink reservoirsfor coating and forming the relatively long signal wirings 5 with aconductive ink. More specifically, when the conductive ink dropped alongthe space having the width c for forming the wirings 5 is too large inquantity, the conductive ink flows into the signal terminal part 13, andwhen it is too small in quantity, the conductive ink is supplied fromthe signal terminal part 13; thus, the signal terminal part 13 serves toform the upper electrodes 5 with an appropriate quantity of conductiveink (FIG. 7). By forming the semiconductor film 7 on the electrodesubstrate with the same arrangement, techniques and materials as thosein Example 3, m×n pieces of thin film transistors are formed at theintersections between the m pieces of gate wirings 2 and the n pieces ofsignal wirings 5 (FIG. 8). Further thereon, a protective film 14 isformed, and thereafter, through holes 15 are formed by removing theprotective film from above the pixel/source electrode 6, gate terminal11, and signal terminal 13. For the purpose of forming the protectivefilm and the through holes, for example, silicon nitride or siliconoxynitride is formed with a plasma chemical vapor deposition method at asubstrate temperature of 150° C. or higher, and is subjected to adry-etching processing based on a photolithography method with SF₆ as anetching gas. When the through holes are formed, a small displacement oftheir positions does not cause a serious problem, so that thephotoresist may be printed to form the through holes. Alternatively, theprotective film and through holes can be formed en bloc by printingafter coating and pre-baking of an organic film made of a photosensitivepolyimide or the like and subsequent mask exposure and development. Whenthe printing production method described in Example 3 and thisprotective film/through hole printing production method are used incombination, an active matrix thin film transistor substrate can beformed in which the gate wiring/electrode 2 and the signal wirings/pixelelectrodes 5 and 6 are disposed in a manner self-aligned with each otherthrough the insulating film 3 interposing therebetween only by usingprinting methods without using a photolithography method. Alternatively,needless to say, when the lower electrode 2 is finely fabricated with aphotolithography method, the upper electrodes 5 and 6 can also be finelyformed as an inversed pattern of the pattern of the lower electrode 2,and a high-definition active matrix thin film transistor substrate canthereby be formed.

EXAMPLE 5

In the present example, a display device using the active matrix thinfilm transistor substrate of the present invention will be describedwith reference to FIG. 14 showing a plan view and a sectional view ofthe main device configuration. A gate scanning circuit 17 is connectedto a gate terminal 11 of an active matrix thin film transistor substrate16, and a signal circuit 18 is connected to a signal terminal 13, with aTAB (Tape Automated Bonding) method or a COG (Chip on Glass) method; andboth of these circuits are further connected to a control circuit 19.Display elements 20 each are sandwiched between a pixel electrode of theactive matrix thin film transistor substrate 16 and a counter electrode21. The thin film transistor, connected to the gate wiring/electrodeapplied with a scanning voltage output from the gate scanning circuit17, is operated, the signal voltage supplied from the signal circuit ina manner synchronized with the scanning voltage is applied to the pixelelectrode connected to the thin film transistor, and the displayelements undergo a so-called linear sequential drive to operate thedisplay device. To the configuration of the thin film transistorsubstrate of the present example, capacitance driven elements such asliquid crystal display elements or electrophoresis elements can beapplied as the display elements 20. In the case of theIn-Plane-Switching liquid crystal display device, as is well known, thecounter electrode 21 is disposed in the thin film transistor substrate,so that the configuration is different from the present figure, but theabove described display elements can be applied basically in the samemanner. On the other hand, in the case of current driven displayelements for an organic electroluminescence device (OLED) or the like,the above described display elements can also be applied, if a wellknown active matrix thin film transistor substrate for driving OLED isfabricated according to the present invention; this display device canbe applied to the flat display for cellular phones, flat televisions,laptop PCs and the like. Alternatively, needless to say, the thin filmtransistor of the present invention can be applied to any semiconductordevices, other than display devices, using thin film transistors, suchas RFID devices typified by contactless IC cards.

EXAMPLE 6

In the present example, the backside exposure method of a photosensitivelyophobic film and the device configuration will be described withreference to FIG. 15 showing the schematic configuration thereof. Thereis prepared a substrate 1 on which a lower electrode 2 and an insulatingfilm 3 are layered sequentially in this order and thereafter aphotosensitive lyophobic film 4 is dip-coated. In this case, thephotosensitive lyophobic film 4 is adhered to the backside of thesubstrate 1 and to the surface of the insulating film 3. A photocatalystfilm 24 typified by titanium oxide having a thickness of about 200 nm,formed on the surface of a supporting plate 23 made of aluminum or thelike with a built-in heating mechanism such as a sheathed heater, isadhered to the above described substrate 1 (FIG. 15 (a)). In order toimprove the adhesion, it is effective to interpose a rubber sheet madeof PDMS or the like between the supporting plate 23 and thephotocatalyst film 24 as a cushion. Irradiation from the backside of thesubstrate 1 with the light having the wavelengths transmitting throughthe substrate and the insulating film to be absorbed by thephotocatalyst film produces hole carriers having a strong oxidizingpower on the surface of the photocatalyst film 24. These hole carriersdirectly decompose the adjacent photosensitive lyophobic film, and thephotosensitive lyophobic film 4 is fabricated so as to have a patternapproximately the same as that of the lower electrode 2. In thisconnection, preliminary heating of the photocatalyst film 24 with theheating mechanism to 100° C. or higher improves the pattern fabricationaccuracy of the photosensitive lyophobic film 4 to allow fabrication toattain a minimum pattern width of 3 μm. This is conceivably because whenmoisture attaches to the surface of the photocatalyst film, the holecarriers oxidatively decompose the water to produce OH radicals, and theOH radicals indirectly decompose the photosensitive lyophobic film, sothat the OH radicals drift and migrate in the space between thephotocatalyst film 24 and the photosensitive lyophobic film 4 todecompose and remove even the photosensitive lyophobic film 4 in alight-shielding region. When adsorbed moisture is preliminarily removedfrom the surface of the photocatalyst film by heating, the indirectdecomposition process caused by the OH radicals does not work, but onlythe direct decomposition process by the hole carriers having a shortmigration distance does work, improving the pattern fabrication accuracyof the photosensitive lyophobic film 4. Additionally, as compared to thephotocatalyst film 24 having an irregular surface, the photocatalystfilm 24 having a flat and smooth surface improves the adhesion betweenthe photocatalyst film 24 and the photosensitive lyophobic film 4, andthe pattern fabrication accuracy and efficiency are thereby improved.

As described in Example 1, when titanium oxide is used as aphotocatalytic material, the exposure wavelengths are 400 nm or less,and accordingly materials transmitting these wavelengths are used forthe substrate 1 and the insulating film 3. When avisible-light-responsive photocatalytic material such as nitrogen-dopedtitanium oxide is used, the exposure wavelengths are 600 nm or less, andaccordingly materials transmitting these wavelengths are used for thesubstrate 1 and the insulating film 3. In the present method, nophotocatalytic material is used in the insulating film, so that organicmaterials having the above described conditions can be used for theinsulating film 3 and the semiconductor film 7. When the photosensitivelyophobic film is fabricated with the present method, the light havingthe wavelengths that do not directly process the photosensitivelyophobic film can be used for the backside exposure. Consequently, asfor the materials for the electrode substrate, in relation to afluorinated alkyl silane coupling agent having a photosensitivewavelength of 300 nm or less to be used as the photosensitive lyophobicfilm 4, a material nontransparent to the photosensitive wavelengths ofthe photosensitive lyophobic film can be used for at least one of thesubstrate and the insulating film, for example, so that a glasssubstrate such as Corning 1737 is used for the substrate 1 or an organicmaterial such as PVP is used for the insulating film 3.

EXAMPLE 7

In the present example, an m-row n-column active matrix thin filmtransistor substrate and a method for producing the substrate concernedwill be described, similarly to Example 6, with reference to FIGS. 17 to22 showing the plan views of the substrate concerned. The most prominentfeature of the present example resides in that, in a rectangle 8, asshown in the figure, a sawtooth-like shape is adopted for each of thethree sides other than the left side on which a semiconductor film 7 isformed. This is a design to prevent the false operation caused by theelectric interference of an adjacent thin film transistor, as will bedescribed later. On a plurality of gate wirings 2 (FIG. 17) composed ofthe rectangles 8 and the connection parts 9 and disposed adjacently toeach other, an insulating film 3 and a photosensitive lyophobic film 4are layered sequentially in this order (not shown in the figure), andthe photosensitive lyophobic film is fabricated into a shapeapproximately the same as that of the gate wirings 2 with the backsideexposure (FIG. 18). By using an appropriate quantity of a conductiveink, signal wirings 5 and pixel electrodes 6 are formed. In this case,the signal wirings 5 and the pixel electrodes 6 are formed in lineshapes or rectangle shapes in the same manner as in FIG. 7, inparticular, so as to for the ends of each of the signal wirings 5 andthe pixel electrodes 6 to contact the tips of the sawtooth-like upper,lower and right sides of any one of the rectangles 8. This is becausethe liquid conductive ink to be used for formation of the signal wirings5 and the pixel electrodes 6 is more stable in energy in the case wherethe ink does not penetrate into the recessed portions of thesawtooth-like shape and thus the surface area of the ink is decreasedthan in the case where the ink penetrates into the recessed portionsconcerned to increase the surface area thereof. Consequently, ascompared to the capacitance formed between the pixel electrode 6 and theleft side of the rectangle 8, the capacitance formed between the pixelelectrode 6 and the upper, lower and right sides of the rectangle 8becomes negligibly small. Similarly, as compared to the capacitanceformed between the signal wiring 5 and the left side of the rectangle 8,the capacitance formed between the signal wiring 5 and the right side ofthe rectangle 8 becomes negligibly small. Consequently, each of thesignal wirings 5 electrically strongly couples, through the left side ofthe rectangle 8, only with the pixel electrode 6 with which the signalwiring concerned is in contact on the right side thereof in the figure,and the portion thereof in contact with the other sawtooth-like ends ofthe rectangle 8 can decrease the electric coupling. A thin filmtransistor is formed by coating and forming a semiconductor film 7 onthe left side of the rectangle 8, in the same manner as in FIG. 8. Inthe present example, description is made particularly on the method inwhich the semiconductor film 7 is formed by deposition selectively onlyon the left side of the rectangle 8. For this purpose, as shown in FIG.20, the signal wirings 5 and the pixel electrodes 6 are formed bycoating, and thereafter, by partial irradiation with ultraviolet lightfrom the surface by using a photomask, the photosensitive lyophobic filmis removed from the portion 8-1 other than the left side of therectangle 8. This substrate is set in a vacuum deposition apparatus, andpentacene semiconductor molecules are deposited at a substratetemperature and the pressure appropriately adjusted. As a result, thesemiconductor film 7 composed of pentacene semiconductor molecules isselectively formed only on the left side 8-2 of the rectangle 8 (FIG.21) which is still coated with the photosensitive lyophobic film. As forthe details of this selective growth, for example, S. Verlaak et al.,Physical Review, B68, 194509 (2003) may be referred to. A TFT substratesimilar to that in Example 6 is completed by forming a protectiveinsulating film (not shown in the figure) on this semiconductor film 7and forming the through holes 15 on the pixel electrodes and the like.

As described above, according to the present invention as described inthe individual examples, the upper electrodes having the inversedpattern of the pattern of the lower electrodes are formed by utilizingthe lyophilic/lyophobic regions formed by the photosensitive lyophobicfilm on which the lower electrode pattern is transferred by utilizingthe lower electrode itself as the photomask, and consequently, the upperelectrodes and the lower electrodes are formed in a self-aligned mannerto be aligned with each other, and no misalignment is caused even whenthe lower electrodes are formed with a printing method. Consequently, byusing a printing method, there can be formed an electrode substrate inwhich the upper electrodes and the lower electrodes are accuratelyaligned with each other through an insulating film interposingtherebetween. If the pattern of the lower electrode is devised so thatthe nonpenetration effect of conductive ink and the crosslinkage effectof conductive ink may be utilized when the upper electrodes are coatedand formed with a conductive ink, wirings/electrodes disposed in aself-aligned manner intersecting with each other through an insulatingfilm interposing therebetween can be formed with a printing method.

FIG. 16 illustrates the effect of reducing the number of steps forproducing an electrode substrate on the basis of a printing method.According to a conventional lithography method, a formation of anelectrode requires 8 steps, and 19 steps are required in total, butaccording to the printing method of the present invention, an electrodesubstrate can be produced in a half or less number of steps, namely, in7 steps, and an effect of productivity improvement is definitelyattained.

INDUSTRIAL APPLICABILITY

As described above, the electrode substrate according to the presentinvention and the thin film transistor using the same are suitable foruse in semiconductor devices such as low-price display devices.

1. An electrode substrate in which a lower electrode, an insulating filmhaving lyophobic/lyophilic regions on a surface thereof and an upperelectrode are layered sequentially on a substrate, characterized inthat: the lower electrode has a pattern approximately aligned with thatof the lyophobic region on the surface of the insulating film; the upperelectrode is formed mainly on the lyophilic region other than thelyophobic region on the surface of the insulating film; and the upperelectrode has a self-aligned pattern in which the pattern of the lowerelectrode is approximately inversed.
 2. A thin film transistorcomprising the electrode substrate according to claim 1 and asemiconductor film, wherein the electrode substrate is characterized inthat a gate electrode is formed as the lower electrode, and a sourceelectrode and a drain electrode are formed as the upper electrode on twoor more areas of the lyophilic region separated by the lyophobic regionformed on the surface of the insulating film in a pattern approximatelyaligned with that of the lower electrode so that the upper electrodehas, in a self-alignment manner, an approximately inversed pattern ofthe gate electrode as the lower electrode, the thin film transistorbeing characterized in that: the semiconductor film is formed so thatthe semiconductor film covers and extends across at least a part of eachof the following members on said electrode substrate: the sourceelectrode, drain electrode and the surface of the insulating film (thegate electrode region) interposing therebetween.
 3. An active matrixthin film transistor substrate comprising the electrode substrateaccording to claim 1 and thin film transistors, wherein in the electrodesubstrate, a plurality of gate wirings/electrodes are formed as thelower electrode, and a plurality of signal wirings, a plurality ofsource/drain electrodes and a plurality of pixel electrodes are formedas the upper electrodes on a plurality of areas of the lyophilic regionseparated by the lyophobic region formed on the surface of theinsulating film in a pattern that is approximately aligned with that ofthe lower electrode, wherein the semiconductor films of the thin filmtransistors are formed so that the semiconductor films extend to coverastride at least a part of each of the following members on theelectrode substrate: the source electrodes, drain electrodes andlyophobic regions (gate wiring/electrode regions), on the surface of theinsulating film, interposing between the source electrodes and the drainelectrodes, and wherein the thin film transistors are each disposed atany one of the intersection portions between the gate wiring and signalwiring.
 4. The active matrix thin film transistor substrate, accordingto claim 3, characterized in that: a plurality of gatewirings/electrodes are formed adjacently to each other as the lowerelectrodes, wherein the gate wirings/electrodes are characterized byhaving a shape in which a plurality of adjacently disposed ring-shapedrectangles each having an opening are connected to each other at leastat one or more locations; signal wirings and source/drain electrodes arecontinuously formed as the upper electrodes in a self-alignment mannerin the spaces between said rectangles so as to extend across theconnection parts between said rectangles; and the pixel electrodes eachare formed in one of the ring-shaped openings of said rectangles.
 5. Theactive matrix thin film transistor substrate, according to claim 4,characterized in that the widths of the connection parts connecting theplurality of rectangles, forming individual gate wirings/electrodes,each having one of the openings and the widths of the spaces between theplurality of gate wirings/electrodes are smaller than the separationsbetween the plurality of rectangles each having one of the openingsforming said individual gate wirings/electrodes.
 6. A liquid crystal,electrophoresis, or organic electroluminescence display device,characterized by using the thin film transistor substrate according toany one of claims 3 to 5 as an active matrix switch.
 7. An RFID device,characterized by using the thin film transistor according to claim 2 asat least a part thereof.
 8. The electrode substrate, thin filmtransistor and active matrix thin film transistor substrate, accordingto claims 1 to 3, characterized by using a photosensitive lyophobicmonolayer film comprising a carbon chain in which at least a partthereof is terminated with a fluorine or hydrogen atom as aphotosensitive lyophobic film.
 9. A method for forming the electrodesubstrate, thin film transistor, and active matrix thin film transistorsubstrate according to claims 1 to 5, comprising: laminating a lowerelectrode, an insulating film and a photosensitive lyophobic monolayersequentially in this order on a substrate; removing the photosensitivelyophobic monolayer from the surface of the insulating film at portionsnot masked by the gate electrode by backside exposure to form alyophilic region, wherein the photosensitive lyophobic monolayer film isprocessed so that the pattern thereof is approximately aligned with thatof the lower electrode; and coating and baking a liquid material(conductive ink) containing at least one of a metallic ultrafineparticle material, a metal complex and a conductive polymer to form anupper electrode mainly on said lyophilic region.
 10. A method accordingto claim 9 for forming the electrode substrate, thin film transistor,and active matrix thin film transistor substrate according to claims 1to 5, comprising: adjacently disposing a substrate, on a surface ofwhich a photocatalytic material comprising titanium oxide,nitrogen-doped titanium oxide, strontium titanate or the like thatdisplays photocatalysis with a light having a wavelength that transmitsthrough the substrate, insulating film and photosensitive lyophobicfilm, but does not transmit through the lower electrode, on a surface ofa light-transmitting substrate on which a light-nontransmitting lowerelectrode, a light-transmitting insulating film and a photosensitivelyophobic film are layered sequentially in this order; and decomposingand removing the photosensitive lyophobic film by the photocatalysis bythe photocatalytic material that absorbs the light transmitting throughthe substrate, insulating film and photosensitive lyophobic film by thebackside exposure to be subjected to pattern fabrication into a patternhaving a shape approximately the same shape as that of the lowerelectrode.
 11. The electrode substrate, thin film transistor, and activematrix thin film transistor substrate according to claims 1 to 5,characterized in that at least one of the substrate and the insulatingfilm is formed with a material that does not transmit a light having aphotosensitive wavelength of the photosensitive lyophobic film.